Airlines are running out of gas. Literally.

High fuel prices are hammering the airline industry. I know that, and that all these annoying surcharges recently announced--for luggage, for drinks--are attempts to somehow make up for the extra fuel costs.

What I didn't know until yesterday was that airlines are also saving money on fuel by simply not filling up the tanks as high as they ought to. The FAA requires that an aircraft carry enough fuel to reach its destination and its most distant alternate airport, plus 45 minutes worth. It's not to the airline's advantage to carry any more than the minimum requirement--more fuel means a heavier plane; a heavier plane gets worse mileage.

Of course, the calculations are based on estimates--estimated passenger weights, estimated luggage, estimated speed. And since my experience yesterday, I'm thinking the airlines are estimating a little low.

I flew from San Francisco to Newark on a Continental 737. Great weather on both ends, only a little turbulence. A lovely flight, actually, best I've had in a long time; the flight attendants were cheerful, passengers got two drink services and a bagel-and-egg sandwich without charge.

A little more than four hours into the flight, the pilot reported that we'd be landing about half an hour ahead of schedule, and flight attendants began collecting trash in preparation for our approach. Perhaps ten minutes later the pilot announced that we'd have to slow down a little to get in line for landing, but we'd still get in well ahead of schedule. I was thrilled; this would be my first flight in at least a year that landed on time, perhaps I could call a friend for dinner.

And then, just a few minutes later, the pilot came on the P.A. system again. "Uh, folks, we're going to make a quick stop for refueling." Huh? Passengers looked at each other in surprise. Flight attendants passed rapidly through the cabin checking seat backs and tray tables and strapped themselves in. Minutes later, we landed at Stewart Air National Guard Base, less than 100 miles from our destination. After a long taxi past National Guard cargo planes, we parked and waited for the fuel trucks.

I was flabbergasted. I've logged a lot of airline miles over the years; I've never been on a flight that ran out of gas. The pilot blamed the problem on air traffic delays; but from what he had said the delay seemed minimal; certainly not enough to eat up the

45-minute reserve the FAA requires. I wondered about the fact that we'd gotten so far ahead of schedule--likely we'd been flying a little faster than is optimal for fuel conservation. I also looked around me at the planeload of European tourists heading home, and wondered if they'd been taking advantage of the cheap dollar and ended up bringing back a lot of extra luggage.

Turns out, though, that the Department of Transportation recently singled Continental out for having the most of what it calls "minimum fuel declarations" into Newark airport last year--96, more than twice the amount it made the previous year. Declaring "minimum fuel" flags the air traffic controllers that, if incoming planes need to be delayed, they shouldn't delay this particular flight too much. The Department of Transportation also found out that Continental has been pressuring pilots to cut back on the amount of fuel they carry, for ultimately the pilot makes that decision. In October, the airline sent out a memo to pilots pointing out that "adding fuel indiscriminately without critical thinking ultimately reduces profit sharing and possibly pension funding." Gee, ya think that's why I ended up sitting on a deserted runway for an hour and a half?